Help please, UPDATE
 

Alright so, my 04 dodge ram 1500 5.7 Hemi quad cab with a colt air intake, intake manifold spacer on a remanufactured engine 4000 miles ago which is misfiring. I have took out the good ol code scanner. The original codes were system too rich and miss in cylinder 3. I checked sparks, wires and coils all checked out. Did a swap of everything to a different cylinder. Still had miss in 3. Two days later it went from miss in 3 to random miss. Now it has o2 high voltage and low voltage, random miss and every now and then rich system. I have checked egr, replaced crank sensor, checked injectors, checked all fuses and relays, spark, wires, coils, alternator, battery, throttle body, and all connectors to those items. Everything checked out. I am not sure where or what to check next. Also it all started when when cold driving and refused to shift into a higher gear then stalled out. Recallebrated throttle then started to miss.

truck now only shows two codes p0174 and p0175 misfire went away a few days ago and has not shown up since.

Maybe start with a compression test ? Especially cylinder 3 ?

pull valve cover to check for broken valve spring.... good luck

How old/what brand are the 02 sensors?

I have the same 2004 1500 5.7. I had something very similar happen to me. I had random multiple misfire code, EGR valve code, and rich oxygen sensor code. I figured rich O2 code was because it was misfiring. Fuel is not burning, make sense that the system see it as rich.

I had a very knowledgeable mechanic tell me that the 5.7 Hemi plug wires go out frequently compared to most because they are ran over the hot intake in a some what poor design. With the HEMI I believe it gets hotter as well with the design of the piston and combustion chamber. The hot intake breaks them down faster. I didn't believe him because I inspected the wires and visually they looked fine. Ans also because I was hesitant to replace 16 plugs and wires. I ended up giving in, Replacing the EGR valve didn't work, so I replaced all 16 plugs and wires. What a ball buster, and not exactly easy on my wallet. But what do you know, the mechanic was right. Fixed the problem, runs like a champ now.

Good luck.

the plugs and wires were replaced when I got the remanufactured engine 4000 miles ago.

I am not sure i will haft to check that tomorrow in the light

I have never taken off the valve cover before, any tips? Should I be prepared for a mess?

I will put it on the list for tomorrow.

Let the engine cool, (and the oil drain back to the pan) and it shouldn't be very messy at all.